The purpose of this project is to examine the subcellular and extracellular structure of nerve and muscle and relate such structure to function. Electron microscopy in TEM, STEM and analytical electron beam probe modes, such as EELS and EDAX, determination of proteins contributing to these structures and structural modeling are methods used in this study. The following structures are probed: 1) Neuroplasmic lattice, 2) neurofilaments, 3) microtubules, 4) axolemma, 5) glial cell membranes, and 6) myofilaments. Methods developed and used in this study are: 1) Stereoscopic imaging, 2) optical autocorrelation, 3) fast Fourier transformation (FFT) of STEM video images, and 4) STEM video image filtering and image enhancement using reverse Fourier transformation. Video imaged light microscopy is used to study living neurons in differential interference contrast. A new method was developed for direct visualization of particle velocity distribution. By viewing image pairs separated by an appropriate time interval in sequential recording of the subject, the positive or negative parallax arising from particle motion results in the binocular image of a particle being perceived as raised or lowered relative to an immobile background plane depending on its direction of movement. The degree of perceived elevation is proportional to particle speed. Using this method, measured particle movement during axoplasmic transport in squid axons ranged from 0.05 to 0.75 Mum/sec. Morphological studies using electron microscopy of sections of Myxicola giant axons showed that the thickness of the Schwann cell layer is about 10 Mum and the thickness of the periaxonal space is from 10-20 nm. These values were shown to be consistent with electrical studies of periaxonal K+ accumulation using voltage clamp methods.